(1) Field of the Invention
The present invention relates to a method and bacterial compositions which use cells of Lactobacillus sp. AS-1 (ATCC No. 55326) to inhibit spoilage in foods. In particular, the present invention relates to a lactic acid producing bacterium which can be used to prevent spoilage in foods at refrigeration temperatures and which does not produce significant amounts of lactic acid in the food.
(2) Prior Art
Lactic acid bacteria have been used to inhibit pathogens and spoilage bacteria in milk and other foods as evidenced by U.S. Pat. Nos. 4,599,313 to Gonzalez and 4,912,047 to Matrozza and by White et al., J. Food Protection 42, 51-54 (1979) and Griffiths et al, J. Soc. Dairy Tech. 44, 24-29 (1991). A paper was presented in a meeting of the Institute of Food Technologists in June, 1991 describing the use of lactic acid bacteria in milk to inhibit pathogens and spoilage. The specific strain used was not identified or described. The bacterial compositions described are effective; however, there is a need for a more effective bacterial composition, particularly one for use in raw milk. One particular problem is that most lactic acid bacteria of the prior art produce sufficient lactic acid even at low temperatures so as to render raw milk unsuitable for pasteurization. Heating raw milk in pasteurizer units when the milk pH is 5.0 or below causes deposit of denatured milk proteins on heating surfaces.
In some countries several days may elapse before raw milk is pasteurized. During that time pathogens and spoilage bacteria can grow and render the milk unfit for its intended use. The legal bacterial count of raw milk is 1.times.10.sup.5 -3.times.10.sup.5 (100,000 for individual producers--300,000 for co-mingled milk) colony-forming units (CFU)/ml. Psychrotrophic bacteria grow at low temperatures (4.degree.-5.degree. C. or 40.degree.-41.degree. F.) and degrade proteins and fat of raw milk and enzymes from these bacteria survive even ultra high temperature (UHT) pasteurization.
Temperature abuse occurs and spoilage and pathogenic bacteria grow reducing quality and safety of the raw milk. Raw milk is stored at 40.degree. F. before pasteurization for transportation to dairy plants. There may be a short supply of raw milk to large dairy plants and thus there is a need for a reliable and effective method for preserving the raw milk.
The problems with raw milk are present with other refrigerated foods where temperature abuse can occur. Fluid or semi-fluid dairy products, such as yogurt, sour cream, cream and cottage cheese particularly have problems.